Natural Air Drying of Binned Soybeans

Figure 1. The various sized bins on this farm allow for storing different moisture contents. Wetter, more dense grain works well in the smaller bins so that more airflow per bushel can be delivered. Drier grains where aeration is the primary need store well in the larger bins. If the grain is wetter, drying grain in layers can help increase airflow per bushel. (Photo by Paul Jasa)

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A grain drying program was used to estimate the time it would take to dry soybeans (see Table 1). It estimated the days to dry soybeans in a grain bin using natural air and 1 cubic foot per minute per bushel of grain in the bin. When drying in the bin, avoid using the stirator as it can damage soybeans.

As you can see in Table 1, weather conditions are a huge factor in how long it takes to dry grain.

Table 1. Days required to dry soybeans to 13% moisture with 1 cfm/bushel airflow, using natural air drying. Assumes exhaust air has 85% relative humidity.

Air Temperature*

Initial Moisture (%)

60°F

14

15

16

17

18

19

Relative Humidity

Drying Time (days)**

60%

4.6

9.2

14.0

18.9

23.9

29.0

50%

3.4

6.9

10.5

14.1

17.8

21.7

40%

2.7

5.4

8.2

11.1

14.1

17.1

30%

2.2

4.4

6.7

9.1

11.5

14.0

Air Temperature

Initial Moisture (%)

50°F

14

15

16

17

18

19

Relative Humidity

Drying Time (days)

60%

6.0

12.1

18.3

24.7

31.3

38.0

50%

4.3

8.7

13.2

17.8

22.5

27.4

40%

3.4

6.8

10.3

13.9

17.6

21.4

30%

2.8

5.6

8.4

11.4

14.4

17.5

Air Temperature

Initial Moisture (%)

40°F

14

15

16

17

18

19

Relative Humidity

Drying Time (days)

60%

6.7

13.5

20.5

27.7

35.0

42.5

50%

4.9

10.0

15.1

20.4

25.9

31.4

40%

3.9

8.0

12.1

16.3

20.7

25.1

30%

3.3

6.6

10.0

13.5

17.1

20.8

*The temperatures indicated — 40°F, 50°F, and 60°F — are the average of the high and low for the day. ** Drying time is proportional to airflow. To estimate drying time for airflow values other than 1 cfm/bu, divide the drying time in the table by the cfm/bu for your bin. For example, if your airflow is 1.25 cfm/bu and the estimate in the table is 10 days, your estimated drying time would be 10 days/1.25 = 8 days.